Positron-Emission Tomography (PET) and emission computed axial tomography (ECAT) offer unprecedented opportunities to visualize and measure in vivo organ metabolism. Our current interest centers on the brain, perhaps the least accessible region of the body to non-invasive diagnostic probes. One desirable goal of image processing in this field of interest is determination of volumetric metabolic activity from collections of scan plane data. Our work on data spreading and attenuation due to finite object size (partial voluming) has made specification of object recovery as a function of system resolution possible. Thus, axial sampling can be chosen to maintain visibility of, or activity recovery from, objects of a selected minimum size through a set of scan planes. With such choices, it is possible to relate scan plane data to a three dimensional model of the brain robustly. Use of such a model can allow meaningful comparisons of data taken from subjects with different orientations and locations relative to the PET or ECAT frame of reference. Another, more ambitious, goal is to make a dynamic model of brain activity. Then, one can use time-series PET or ECAT data to estimate biological quantities in functional compartments. Further analysis allows estimates of the parameters of the kinetic rate equations relating them.